Yeah the issue is how they named the zone internally. Maps will inherit based on the zone name basically: exp02_dun_halls_of_fate_x4_fabled will inhert from anything that's an exact match but shorter so it's probably pulling from exp02_dun_halls_of_fate rather than whatever the x4 version (so I guess it looks for the shortest match when choosing which to inherit rather than the longest match)

Jnils should be able to get exp02_dun_halls_of_fate_x4_fabled to use the existing Lab of Lord Vyemm map.